The preparation of hard copies from soft information using communication sircuitry has been widely practiced with the recent development of information handling techniques and storage and image processing techniques. Furthermore, print photographs of very high quality are provided relatively easily and inexpensively with the development of silver halide photographic materials and development systems that are compact, rapid and simple (e.g., miniature laboratory system). Therefore, there is a large demand to prepare hard copies having a high picture quality, both easily and inexpensively from print photographs.
Conventional methods for preparing hard copies from soft information sources include methods using electric signals or electromagnetic signals, methods which do not employ a photosensitive material such as ink jet systems, and methods using photosensitive materials (e.g., silver halide photosensitive materials or electrophotographic materials). Furthermore, color reproduction techniques include reproduction apparatus based on electrophotographic techniques, laser printers, heat-developing dye diffusion systems using silver halide and pictrography (trade mark of the Fuji Photo Film Co., Ltd.) using an LED.
The methods using a photosensitive material includea means for recording comprising an optical system which emits light corresponding to the image data. Additionally, these methods allow for high resolution or binary recording as well as multi-gradation recording, and advantageously provide an image of high quality. Particularly, the methods using a silver halide color photosensitive materials are advantageous, because the image is chemically formed, as compared with systems using electrophotographic materials.
JP-A-55-13505 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") discloses a color image recording system using a color photographic material, which operates by controlling yellow, magenta and cyan color image formation with three light beams each having different emission wavelengths, such as light beams of green color, red color and infrared.
JP-A-61-137149 discloses a color photographic material comprising at least three silver halide emulsion layers containing conventional color couplers provided on a support, wherein at least two layers are sensitized to the emission wavelength of a laser beam in the infrared region (without exposure to visible light) and also discloses the basic conditions thereof.
JP-A-63-197947 discloses a full color recording material wherein at least three layers of the photosensitive layer units containing color couplers are provided on a support, at least one layer of which is spectrally sensitized to have a maximum wavelength sensitivity longer than about 670 nm that is sensitive to a LED or semiconductor laser beam, such that a color image can be obtained by light scanning exposure and color development. Furthermore, a high-sensitivity, stable spectral sensitizing method and a method for using dyes are also disclosed therein.
When a semiconductor laser is used for the scanning exposure, the exposure device can advantageously be made to be compact and inexpensive. S.H. Baek, et al. reported a semiconductor laser output controlling mechanism of the continuous scanning type for printers and the basic conditions for the operation thereof on pages 245-247 of the preliminary manuscript for the fourth Nonimpact Printing (NIP) International Conference (SPSE) (Mar. 23, 1988).
The methods for preparing hard copies from soft information sources by using a silver halide color photosensitive material are advantages in that a stable image of high quality is obtained as compared with non-sensitive recording methods and methods using electrophotographic materials. However, when using a silver halide photosensitive material, it is difficult to carry out color development in a rapid and simple manner commensurate to the rate of the scanning exposure
Therefore, in order to be practically used in a scanning exposure system, the color development of the full color recording material must be completed in 90 seconds or less to be adaptable to the writing speed of an output device using a semiconductor laser beam.
A silver iodobromide emulsion, a silver bromide emulsion and a silver chlorobromide emulsion are known as silver halide emulsion for use in a silver halide photographic material that is suitable for writing (exposure) with a laser beam Among them, silver halide emulsions having a high silver chloride content are preferred for fast development. However, the above-described patent publications are silent with respect to the case of use a silver chloride emulsion or a silver chlorobromide emulsion having a high silver chloride content, and particularly, a silver chloride content of at least 96 mol %. Additionally, it has been found that the desired rapid processing is not achieved when color photosensitive materials described in the above noted patent publications are used. Furthermore, it has been found that the above-described rapid in color development can not be achieved simply by using a silver halide emulsion having a high silver chloride content of at least 96 mol %.
A silver halide color photographic material which can be subjected to rapid, simple, continuous color development processing, which is suitable for scanning exposure and which is able to provide an image having high quality is highly desired.
Exposure devices using a semiconductor laser for scanning exposure are compact and inexpensive. However, it has been found that the light emission intensity and light emitting wavelength region of semiconductor lasers are unstable in comparison with gas lasers. Particularly, the latitude of modulation of the emission intensity as a function of input current of a semiconductor laser beam having a relatively short wavelength is considerably narrow. Further improvements in silver halide photographic materials are therefore needed to reproduce an image of excellent quality. Firstly, the spectral sensitization wavelength region of each layer of differing color sensitivity must be sufficiently wide (e.g., 40 to 60 nm), and the overlapping of the sensitization wavelength region of each layer of differing color sensitivity is preferably low (e.g., a logarithmic difference of sensitivity of layers of differing color sensitivity at the dominant sensitivity wavelength of at least 0.50 ). Secondly, it is necessary that a stable latent image be obtained with an exposure time of from 10.sup.-4 to 10.sup.-8 seconds, and that the exposure region has a sufficiently linear gradation in a photographic characteristic curve of 0.5 or more, and preferably 1.0 or more (represented by logarithm). Accordingly, a silver halide color photographic material is desired which meets the requirements of the simplicity and rapid color development, and which provides good stability, sensitivity, color separation and gradation.
Furthermore in order to attain rapid simple color development as described above, the photosensitive materials must be thin and must be sufficiently flexible to be easily conveyed through processor. Particularly, when a scanning exposure system employing a laser beam is used, the photosensitive material must have a smooth surface and uniform light reflection characteristics. Furthermore, the production cost must be minimized.
Generally, a substrate obtained by coating both sides of base paper with polyethylene is used as a support for the photographic paper. To obtain supports having a smooth surface, various proposals have been advanced. For example, JP-A-60-67940 discloses a pulp for preparing a base paper for a support, wherein the void volume of pores having a pore size of not greater than 0.4 .mu.m is not less than 0.04 ml/g. JP-A-60-69649 discloses the use of a wood pulp having an average fiber length of 0.4 to 0.9 mm, an average fiber width of not less than 13.5 .mu.m and an average fiber thickness of not greater than 4 .mu.m. JP-A-61-275752 discloses the use of a mixture of natural pulp containing from 5 to 60% of a hydrophobic fiber. JP-A-61-284762 discloses dehydrating conditions for obtaining a wetted paper from a pulp slurry using a two sheet wire paper machine. Furthermore, the applied pressure of a machine calender is used to increase the density of a base paper used as a support for a photographic paper, wherein the base paper is calendered between metallic rollers In addition, the base paper is coated with a polyolefin such as polyethylene generally by an extrusion coating method. Namely, the polyolefin is molten at a high temperature and cast on the surface of the base paper to thereby coat the base paper with the polyolefin. Attempts have been made to thicken the coated polyolefin layer or to increase the pressing pressure during the polyolefin coating in order to improve the smoothness of the support.
However, the above-described techniques used to smoothen the water-resistant resin layer provided on the surface of the support are not satisfactory with respect to the degree of smoothness required for rapid processing, particularly when a scanning exposure system comprising a laser beam as the light source is employed In addition, these techniques are disadvantageous withrespect to cost. Furthermore, when the above described techniques are employed to increase the density of a base paper for a thin support blackening or paper denting tends to occur, and edge staining tends to occur in the rapid color development stage.